1. Field of the Invention
The invention relates to a method for coating a support plate for carrying out functional tests on biological cells, to a support plate for carrying out functional tests on biological cells and to the use of corresponding support plates for carrying out functional tests on biological cells.
In the field of fundamental biological research and in applied biotechnology, for example drug screening or diagnosis, support plates for example of glass or plastic are used, by means of which a multiplicity of studies such as interactions between biological material and chemical/biological substances can be studied. To this end the support plates are generally coated, for example with poly-L-lysin, via which biological material such as biological cells is fixed onto the surface of the support plate. Functional tests can then be carried out on the fixed cells. Support plates configured in such a way are also referred to as biochips. The coating of the support plate with a very wide variety of materials is of crucial importance, since all subsequent steps such as the application of biomolecules, colonization with biological cells and the reproducibility of the functional tests by means of the finished biochip depend thereon.
2. Prior Art
WO 02/02226 A2, which is incorporated herein by reference, discloses a method for coating a support plate, in which polylysin is spotted onto an aldehyde-activated surface of the support plate by means of conventional inkjet technology or contact printing methods. In a subsequent step, extracellular matrix (ECM) proteins are bound covalently to the previously activated polylysin. In order to avoid non-specific binding of cells to the aldehyde-activated surface, aldehyde groups still free inside and above all outside the microspots are saturated. The same treatment is also carried out whenever proteins are bound directly to aldehyde-activated surfaces. The disadvantage of the method is that the saturation of the aldehyde groups is not sufficient to fully prevent non-specific binding of cells.
U.S. Pat. No. 6,548,263 B1, which is incorporated herein by reference, discloses a method which attempts to prevent such non-specific binding of cells on regions outside the microspots loaded with biomolecules. A support plate made of glass, plastic or silicone is chemically modified in this case, for example with aminosilane (3-aminopropyltrimethoxysilane). Proteins which are spotted onto this surface can be bound to the reactive groups of the aminosilane either directly or via hetero-bifunctional groups. Before the binding of the biomolecules takes place, cell-repellent hydrophobic coating is carried out in regions outside the microspots in order to prevent non-specific binding of cells to these reactive groups. The method disclosed here is an elaborate multistage method. A further disadvantage of the method described in U.S. Pat. No. 6,548,263 is that the same site is doubly spotted congruently, which is very difficult in practice since reaching the same microspots requires utmost precision of the equipment, which is not available with most arrayers.
US 2002/0019018 A1, which is incorporated herein by reference, discloses a nitrocellulose-coated support plate in the form of a glass slide, monoclonal antibodies being fixed onto the support plate via the nitrocellulose. Details about the coating method are not disclosed.
Glass carriers which have a nitrocellulose surface are furthermore available on the market. This surface can be saturated by corresponding reagents, in order to avoid non-specific adhesion to cells. The nitrocellulose layer, however, has the disadvantage that biological material to be fixed thereon, for example ECM (extracellular matrix) proteins, is absorbed in a sponge-like fashion owing to the high suction ability of the compact nitrocellulose layer, thereby lost deep in the layer and no longer available for subsequent colonization with biological cells. The adhesion of the cells is relatively weak, even though large amounts of the ECM proteins are cost-intensively used. In order to generate a protein layer which is effective for the cell adhesion and accessible to the cells, unnecessarily high concentrations of proteins must be applied, which is difficult with microarrayers, especially inkjet arrayers.